SeasonalBordetella pertussispattern in the period from 2008 to 2018 in Germany

Background After the introduction of a vaccine againstB. pertussisthe seasonal pattern with the highest number of infections in the spring to summer months changed. Recent studies from around the world suggest thatB. pertussisinfections again follow a seasonal pattern with increased incidence in summer.The aim of this study was to investigate whether respiratory infections caused byB. pertussisin the period from January 2008 to December 2018 also seasonally spread in Germany and if so, when theB. pertussisactivity peaked. Methods We tested 19,031 samples, mainly from Southern Germany, collected in the period from January 2008 to December 2018 using a Multiplex PCR assay. We assessed the number and proportion of samples positive forB. pertussis, stratified by patient's age and month. The seasonal distribution was investigated by plotting the average proportion of positive samples for each month. Results We observed aB. pertussisseasonality with the highest number of positive samples in the months from June until September. In contrast, testing of samples forB. pertussiswas requested most frequently in the period from October until March. The proportion of positive samples increased earlier in adolescents (age 10 to 19) than in other age groups. Conclusions We found a seasonality ofB. pertussisinfections in Germany, which differs from the time when most samples are sent in for testing ofB. pertussis.Our study suggests that clinicians should be more aware ofB. pertussisinfections in the months from June until September to prevent further transmission to vulnerable family members.